The earthquake had a preliminary magnitude of 7.3 and struck in the Pacific Ocean off the coast of Miyagi prefecture at 5:18 p.m., the Japan Meteorological Agency said. The epicenter was 6.2 miles beneath the seabed and 150 miles offshore. The area was shaken by repeated, smaller aftershocks, the agency said.

After the quake, authorities issued a warning that a tsunami potentially as high as 2.2 yards could hit. Sirens whooped along the coast as people ran for higher ground.

Ishinomaki, a city in Miyagi, reported a tsunami 1 yard high, and other towns reported smaller tsunamis.